Rotary joint for fluid

ABSTRACT

A rotary joint for fluids that provides a completely sealed path for the flow of polishing solution and which permits the supply of electricity to a polished surface detector. The rotary joint of the present invention is essentially made up of a joint block ( 1 ) and a rotator assembly ( 2 ). To the rotator assembly ( 2 ) rotatably held in the joint block ( 1 ) is attached a polishing pad shaft ( 104 ). Between the joint block ( 1 ) and the rotator assembly ( 2 ) is formed a seal space closed by a pair of seal units ( 5, 5 ), each comprising sealing rings ( 51, 52 ) which rotate in relation to each other. A fluid passage ( 7 ) continuous via a seal space ( 50 ) and running through the joint block ( 1 ) and the rotator assembly ( 2 ) is formed, and a wiring conduit running from an electric source unit ( 3 ) to the polished surface detector on the polishing pad ( 104 ) is also formed. The wiring conduit comprises a rotary connector unit ( 4 ) made up of a casing ( 40 ) and a first connector ( 41 ) supported by the rotator assembly ( 2 ) and a second connector ( 42 ) held by the joint block ( 1 ) with the two connectors ( 41, 42 ) electrically connected to each other and relatively rotatable, electric wiring ( 42   a ) running from the power unit ( 3 ) to the second connector ( 42 ), and electric wiring ( 41   a ) running from the first connector ( 41 ) to the polished surface detector ( 110 ) through a wiring conduit ( 24 ) formed in the rotator assembly ( 2 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to rotary joints for fluids, and morespecifically to rotary joints which allow solid-liquid mixture fluids,including slurry fluids (such as polishing solutions for polishing thesurface of a silicon wafer by a chemical mechanical polishing technique,CMP for short) and corrosive fluids, to flow through the relativelyrotating components and which can be connected to a monitoring apparatusfor checking the polished surface state of the silicon wafer.

2. Description of the Prior Art

An apparatus for polishing the surface of silicon wafer by CMP to whichthis invention relates was recently developed. The apparatus, as shownin FIGS. 5 and 6, comprises: a rotary table 102 that rotateshorizontally; a pad shaft support block 103 which moves back and forthand up and down; a polishing pad shaft 104 which, held by the shaftsupport block 103, is forced to rotate; a slurry fluid feeding anddischarge passage 105 formed on the non-rotary side in the pad shaftsupport block 103; a polishing solution feeding and discharge mechanism107 connected to the slurry fluid feeding and discharge passage 105 forfeeding and discharging a polishing solution 106, for example, aKOH-containing silica slurry to which isopropyl alcohol is added; aslurry fluid feeding and discharge passage 108 on the rotary side whichruns through the polishing pad shaft 104 and opens under a pad head 104a; and a rotary joint 111 which, installed between the pad shaft supportblock 103 and the polishing pad shaft 104, connects the two slurry fluidfeeding and discharge passages 105 and 108 in a way that the twopassages 105 and 108 communicate with each other and are relativelyrotatable.

In that surface polishing apparatus, the silicon wafer 109 is polishedin this manner. First, the silicon wafer 109 is held on the rotary table102, surface 109 a side up, and the polishing pad shaft 104 is moveddown until the pad head 104 a comes into contact with the wafer surface109 a. Then the polishing solution 106 is jetted into between the padhead 104 a and the wafer 109 by means of positive pressure action(discharging operation of the polishing solution pump) of the feedingand discharge mechanism 107. The polishing pad shaft 104 is rotated andmoved back and forth horizontally to polish the wafer surface 109 a.After the polishing is over, the feeding and discharge mechanism 107 isswitched over to negative pressure action (suction action of thepolishing solution pump) to suck and discharge the residues of thepolishing solution 106 into the slurry fluid feeding and dischargepassages 105 and 108. That is, care is taken so that the residues of thepolishing solution 106 in the slurry fluid feeding and dischargepassages 105 and 108 may not drop on the polished surface of the wafer,and that is effected by switching the passages 105 and 108 from thepositive pressure mode to the negative pressure or dry mode.

The rotary joint 111 mounted in that surface polishing apparatus isconstructed as follows. A joint block mounted on the pad shaft supportblock 103 and a rotator assembly fixed on the polishing pad shaft 104are connected in a manner which permits relative rotation of the two.Within the joint block is formed a first fluid passage section which isconnected to the slurry fluid feeding and discharge passage 105 on thenon-rotary side. On the rotary side, a second fluid passage section isformed in the rotator assembly and is connected to the slurry feedingand discharging passage 108. A space formed between the opening ends ofthe two fluid passage sections is sealed by seal units placed betweenthe relatively rotating faces of the joint block and the rotatorassembly. An example of such seal is a one in which relatively rotatingparts of the joint block and the rotator assembly have sealing faces tobe brought into contact with and pressed against each other, or an endface contact-type mechanical seal placed therebetween.

The rotary joint 111 of such a design presents many problems. That is,the polishing solution 106 is a slurry fluid containing abrasive grains.Those abrasive grains tend to intrude into and be deposited between thesealing faces (in the case of a mechanical seal, the opposing end facesof the two seal rings), making it difficult to maintain good sealingperformance for a long period. A solid-containing slurry fluid, thepolishing solution 106 wears out the seal faces fast, shortening thelife of the seal. In the case of a mechanical seal, because the metallicparts such as a spring to thrust one seal ring against the other sealring are exposed in the fluid passage, the solid matter in the polishingsolution 106 comes into contact with the metallic parts. As a result,the abrasive grains in the polishing solution 106 impact against andremove microscopic protrusions on the surface, thus generating metallicparticles or dust. The metallic particles are adsorbed to matter in theslurry fluid, thereby generating metallic ions. In the case of acorrosive fluid, the metallic particles could be corroded. If suchmetallic particles and dust or particles removed from the seal faces bywear are mixed with the polishing solution 106 and blasted from the padhead 104 a, it will naturally have undesirable effects on the polishingof the wafer surface 109 a. The entry and deposition of abrasive grainsbetween the seal faces, the wearing of the seal faces, and the likeoccur noticeably when slurry feeding and discharging passages 105 and108 are switched over from positive pressure mode to negative pressureor dry mode as mentioned above. Especially in dry mode, the seal contactfaces could be heated and subjected to seizure because of frictionalheat. As the intrusion and deposition of abrasive grains, wear ofsealing faces, etc. affect the sealing performance, polishing solution106 can leak through the seal faces, contaminating the wafer surface 109a, or get into the bearing placed between the joint block and therotator assembly, hindering rotation of polishing pad shaft 104. Goodpolishing then becomes difficult to achieve.

In recent years, meanwhile, higher precision surface polishing has beendemanded in accordance with a recent trend toward high integration. Toraise the precision of polishing a wafer surface 109 a, it is desirableto check and know the state of the wafer surface 109 a during polishingand to control the polishing conditions including the polishing rate ofthe pad head 104 a. To be specific, it is preferable to provide a padhead 104 a with an appropriate polished surface detector 110 such as amonitor at the place indicated by the broken line in FIG. 6. The stateof the wafer surface 109 a is checked by detector 110 in real-time so asto control the polishing conditions properly on the basis of thedetected surface state. To mount such a polished surface detector 110 inthe rotating member pad head 104 a, however, it is necessary to form awiring route from the power source unit (including a display unit suchas a monitor display apparatus to show the finding detected by thepolished surface condition detector 110 and an operation panel andcontrol panel to control polishing condition) to the polished surfacedetector 110 through the rotary joint 111 in such a way that theelectric wire will not be twisted or damaged. In the surface polishingapparatus using the aforesaid rotary joint 111, it is impossible to formsuch a wiring route and to provide a pad head 104 a with a polishedsurface detector 110.

Those problems with the rotary joint 111 are encountered not only in theaforesaid surface polishing apparatus but are common to rotary equipmentin which a slurry fluid-like polishing solution or a corrosive fluid hasto be blown between component parts relatively rotating at a rate higherthan a certain level. Such being the case, it has been strongly desiredthat a solution to the problems should be found, but the fact is that norotary joint for fluids has been developed which exhibits a stabilizedsealing performance for a long time.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide arotary joint for fluids which permits smooth flow, without leakage, of aslurry fluid such as a polishing solution or of a corrosive fluidthrough relatively rotating component parts, and allows a surfacepolishing apparatus, etc. to function properly as mentioned above.

It is another object of the present invention to provide a rotary jointfor fluids which permits mounting on a fluid blasting assembly a desiredelectric instrument such as a monitor without causing troubles such aselectric wire twisting, even if one section of a wiring route which runsfrom the power unit to the fluid blasting assembly is subjected torelative rotation, thus allowing the apparatus equipped with this rotaryjoint to function at a top performance level.

It is still another object of the present invention to provide a rotaryjoint for fluids which effectively prevents seal end faces 51 a, 52 afrom being heated with resultant seizure and losing their sealingcapability—the most serious of problems in a rotary joint—therebyensuring a smooth flow of the slurry fluid for a still longer period.

It is a further object of the present invention to provide a rotaryjoint for fluids which keeps a surface polishing apparatus, etc.functioning properly, without causing such problems as wear particlesand corrosion, when a slurry fluid such as polishing solution orcorrosive fluid is allowed to flow, thereby improving the durability ofthis rotary join also.

It is still another further object of the present invention to provide arotary joint for fluids which keeps the rotary connector unit fromvibrating as the rotator assembly turns, thereby improving thedurability of the rotary connector unit and extending the life of thisrotary joint.

These objects are attained by a rotary joint for fluids comprising: ajoint block; a rotator assembly mounted on a fluid blasting assemblywhich is forced to rotate, this rotator assembly held in the joint blockin such a manner that the rotator assembly is allowed to rotate butunmovable in the axial direction; and a rotary connector unit made up ofa connector portion on the stationary side connected to a power sourceunit and a connector portion on the rotary side electrically connectedthereto such that the connector portion on the rotary side is allowed torotate, further having the followings constructions.

A ring-shaped seal space sealed by a pair of seal units disposed side byside in the axial direction is formed between the outer circumference ofthe rotator assembly and the inner circumference of the joint blocksurrounding the rotator assembly concentrically. The joint block has afirst fluid passage section therein with one end opening at the sealspace. The rotator assembly has a second fluid passage section thereinwith one end opening at the seal space and the other end opening at aplace where the fluid blasting assembly is attached. Thus the two fluidpassages and the seal space form a line of fluid passages runningthrough the joint block down to the fluid blasting assembly. Inaddition, the connector portion on the rotary side is mounted in therotator assembly on the same axis of rotation. The wiring conduit thatleads the electric wire connected to the connector portion on the rotaryside to the fluid blasting assembly is formed so as not to cross thesecond fluid passage section. The connector portion on the stationaryside is mounted in the joint block to form a wiring path leading fromthe power source unit to the fluid blasting assembly via the rotaryconnector. Each seal unit comprises: a rotary seal ring and a stationaryseal ring both made of silicon carbide in which the rotary seal ring isfixed to one of the outer circumference of the rotator assembly and theinner circumference of the joint block while the stationary seal ring isheld in the other one of these two and is movable in the axialdirection; a thrusting member which, placed outside of the fluidpassages, pushes the stationary seal ring against the rotary seal ring;and a stopper to prevent the stationary seal ring from rotating whileallowing the ring to move in the axial direction. Furthermore, one ofthe opposing seal end faces of the two seal rings is tapered andsharp-edge-shaped so as to come into linear contact with the other,whereby the seal space may be sealed air-tight with the two seal endfaces rotating relative to one another and sliding on one another. Incase there is concern that the two seal end faces will become heated andsubject to seizure or other such troubles, it is preferred to provideoutside of the sealed space an area for supplying cooling water to coolthe seal end faces of the respective seal units.

It is also desired to form the inside wall of the fluid passage linewith at least one plastic material selected from among polyether etherketone (PEEK), polyethersulfone (PES), and polycarbonate (PC).Alternatively, it is preferred to coat the inside wall of the fluidpassage line with at least one plastic material selected from amongpolytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkoxyvinyl ether copolymer (PFA), and fluorinated ethylene propylenecopolymer (FEP).

In another embodiment, the connector portion on the rotary side isformed from a casing and a first connector fixed therein, while theconnector portion on the stationary side comprises a second connectorrotatably mounted in the casing. At least part of the casing is fittedinto a first housing space formed in the rotary assembly, and a rotationstopper member keeps the casing and the rotator assembly from relativelyrotating. A second housing space may be formed in the rotator assemblythat communicates with the first housing space and the wiring conduit,with a whole of the first connector fitted into the second housingspace.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical, sectional view of one example of a rotary jointfor fluids embodying the present invention.

FIG. 2 is an enlarged view of the core part of FIG. 1.

FIG. 2A illustrates an example in which the inside wall of a secondfluid passage is formed with a coating.

FIG. 3 is a side view of one example of a surface polishing apparatuswith the rotary join installed therein.

FIG. 4 is a vertical, sectional view showing the surface polishingapparatus.

FIG. 5 is a side view of a surface polishing apparatus equipped with aprior art typical rotary joint.

FIG. 6 is a vertical, sectional view showing the core part of theapparatus shown in FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 to 4 show a preferred embodiment of the rotary joint for fluidsaccording to the present invention.

This embodiment concerns an example of a rotary joint of the presentinvention to be installed in an apparatus for polishing the surfaces ofsilicon wafers by CMP techniques. It is understood that as used herein,terms such as “upper” or “above”, “lower” or “under”, and “horizontal”or “vertical” are adjectives applicable only on the drawings in FIGS. 1and 3.

The surface polishing apparatus presented herein is the same as thatdescribed above in construction as shown in FIGS. 3 and 4. That is, theapparatus comprises: a rotary table 102 that rotates horizontally; a padshaft support block 103 which moves back and forth and up and down; apolishing pad shaft 104 or fluid blasting assembly which, held by thepad shaft support block 103, is forced to rotate; a slurry fluid feedingand discharge passage 105 formed on the non-rotary side in the pad shaftsupport block 103; a feeding and discharge mechanism 107 connected to aslurry fluid feeding and discharge passage 105 supplying a polishingsolution 106; a slurry fluid feeding and discharge passage 108 on therotary side which runs through the polishing pad shaft 104 and opensunder a pad head 104 9 ; and a rotary joint 101 which, provided betweenthe pad shaft support block 103 and the polishing pad shaft 104,connects the two slurry fluid feeding and discharge passages 105 and 108in a way that the two passages 105 and 108 communicate with each otherwhile rotating relative to one another. The pad head 104 a is providedwith a polished surface detector 110 such as a monitor unit to watch anddetect the polished surface on a real-time basis so that the polishingconditions such as polishing rate of the pad head 104 a may becontrolled, depending upon the state of the wafer surface duringpolishing.

The rotary joint 101 embodying the present invention comprises: a jointblock 1 to be mounted on the pad shaft support block 103; a rotatorassembly 2 to be mounted on the polishing pad shaft 104; a rotaryconnector unit 4 made up of a connector portion 42 on the stationaryside connected to the power source unit (including a display unit suchas a monitor display apparatus to monitor the findings detected by thepolished surface condition detector 110 and the operation panel andcontrol panel to control the polishing conditions) and a case 40 andconnector portion 41 on the rotary side electrically connected to theconnector portion 42 and linked thereto such that the connector portion41 and case 40 are rotatable; a pair of seal units, that is, an upperseal unit 5 and a lower seal unit 5, provided between the joint block 1and the rotator assembly 2; a cooling unit 6 to cool the seal end facesof each seal unit 5; and a fluid passage line 7 formed in the jointblock 1 and the rotator assembly 2.

The joint block 1 is made up of three parts 10, 11, and 12 connectedintegrally and arranged vertically as shown in FIG. 1. The upper firstpart 10 and the lower or third part 12 are cylindrical in shape andformed out of support portions 10 a and 12 a, respectively, bothprovided with inner circumferential surfaces and connecting sections 10b and 12 b, respectively, both with circumferential surfaces concentricwith, but larger in diameter than, the inner circumferences of thesupport portions 10 a and 12 a, respectively. It is noted that thesupport portions 10 a and 12 a are identical in diameter to the innercircumference, as are the connecting sections 10 b and 12 b. The middleor second part 11 is formed out of a ring-formed wall portion 11 acoupling the connecting sections 10 b and 12 b and a cylindricalretainer portion 11 b extending up and down from the innercircumferential surface of the wall portion 11 a. The retainer portion11 b is concentric with the circumference of the connecting sections 10b and 12 b, and is designed so that the outside diameter is smaller thanthe inside diameter of the connecting sections 10 b and 12 b by aspecific amount. Of those component parts of the joint unit, the secondpart 11 is exposed to the polishing solution 106, as will be describedbelow. At least this second part 11 is formed of a plastic material formachine parts, which is excellent in dimensional stability and thermalresistance and which does not generate particles in contact with theabrasive grains, such as PEEK, PES, or PC. In the present example, PEEKis used. On the other hand, no such consideration is needed for theother constituent parts 10 and 12 of the joint unit, and any materialmay be selected. In the present example, those parts are made of astainless steel with a JIS standards designation of SUS 304.

The rotator assembly 2 is formed out of a cylindrical main part 20; aretainer sleeve 21 fit on and fixed to a middle portion of the main part20; a fixing sleeve 22 fit on and fixed to the main part 20 at the lowerportion; and a flange 23 screwed to the main part 20 at the lower end.

The upper end of the main part 20 comprises a first cylinder 25 and asecond cylinder 26 thereunder. The two cylinders 25 and 26 areconcentric with the axis of rotation of the rotator assembly 2. Theinside diameter of the first cylinder 25 is so designed in accordancewith the outside diameter of a casing 40 of the rotary connector unit 4that the casing 40 can be tightly fit into the interior space of thefirst cylinder 25 or a first housing space 25 a. The rotary connectorunit 4 will be described in more detail below. It is desired that thedepth (vertical length) of the first housing space 25 a should be setnot shorter than one half of the vertical length of the casing 40 sothat at least a lower half of the casing 40 is housed. The secondcylinder 26 is designed to be smaller than the first cylinder 25 indiameter. The inside diameter of the second cylinder 26 is set inaccordance with the outside diameter of the connector 42 so that a firstconnector 41 of the rotary connector unit 4 (which will be detailedbelow) may be just fit into the interior space of the second cylinder26, or a second housing space 26 a. The depth (vertical length) of thesecond housing space 26 a is set so as to house the whole of theconnector portion 41.

The rotator assembly 2 is rotatably held in the joint block in such astate that the component parts of the rotator assembly (that is, themain part 20 and the two sleeves 21 and 22) except for the flange 23 areplace inside the joint block 1 with two bearings 13 and 13 installed—onebetween the second cylinder 26 of the main part 20 and the supportportion 10 a of the joint block 1, and the other between the clampingsleeve 22 and the support portion 12 a. The flange 23 is fixed to thepolishing pad shaft 104 so that the rotator is forced to rotate as thepolishing pad shaft 104 turns. Of those component parts of the rotaryassembly, at least the main part 20 and the retainer sleeve 21 whichcome into contact with the polishing solution 106 (which will bedescribed in detail below) are formed of a plastic material for machineparts, such as that used for the second part 11 of the joint block 1.Examples of such plastic materials are PEEK, PES, and PC. These haveexcellent dimensional stability and thermal resistance and further donot degenerate in contact with abrasive grains. In the present example,PEEK is adopted. On the other hand, any material may be selected for theother constituent parts 22 and 23 of the rotator assembly 2 that are notsubject to such considerations. In the present example, those parts aremade of a stainless steel with a JIS standards designation of SUS 304.

The rotary connector unit 4 is a known one, and is made up of aconnector portion on the rotary side including a casing 40 and a firstconnector 41 fixed thereunder, and a connector portion on the stationaryside comprising a second connector rotatably mounted on the casing 40,arranged so that each electric wire 41 a connected to the firstconnector 41 is kept in constant contact with each correspondingelectric wire 42 a connected to the second connector 42 while theconnectors 41 and 42 rotate relative to one another. The casing 40 andthe two connectors 41 and 42 are circular, with a center which is equalto the axis of relative rotation of the connector 41 and 42. The twoconnectors 41 and 42 are smaller than the casing 40 in outside diameter.The electric wire 41 a of the first connector 41 is connected to thepolished surface detector 110. The electric wire 42 a of the secondconnector 42 is connected to a power source unit 3 including a controlpanel. The casing 40 and the first connector 41 are housed in the firsthousing space 25 a and the second housing space 26 a of the rotatorassembly 2, respectively, in a firmly fitted state. The casing 40 isfixed in the rotator assembly 2 by means of a set screw 43, a rotationstopper member screwed into the first cylinder 25 such that the casing40 is not allowed to rotate relative to the rotator assembly 2. Thesecond connector 42 has a bracket 44 fixed thereon by a set screw 44 a.The second connector 42 is kept from rotating in relation to the jointblock 1 with a stopper pin 45 such as a bolt screwed in the upper end ofthe joint block through an opening 44 b made at the periphery of thebracket 44. One or more than one opening 44 b and stopper pin 45 may beprovided. Engagement of the opening 44 b and the stopper pin 45 ismerely to prevent the second connector 42 and the joint block 1 fromrotating in relation to each other. It is needless to say that whenshift, due to vibration of the rotary assembly 2, of the axis of therotary assembly 2 and the rotary side connector portion 40, 41 from theaxis of the second connector 42 of the stationary connector portionoccurs, the second connector 42 may be moved to reverse such shift. Inthe main part 20, there is formed a wiring conduit 24 running from thefirst and second housing spaces 25 a and 26 a to the polishing pad shaftmounting section, that is, the lower end of the rotator assembly 2. Inthe polishing pad shaft 104, also, a wiring conduit 104 b is formed thatruns from the lower end of the wiring conduit 24 to the polished surfacedetector 110. Thus the electric wire 41 a connected to the firstconnector 41 can be led to the polished surface detector 110 through thetwo wiring conduits 24 and 104 b. Therefore connecting the electric wire41 a to the polished surface detector 110 forms a wiring path from thepower source unit 3 to the polished surface detector 110 through therotary members, that is, the rotator assembly 2 and the polishing padshaft 104. That way, the polished surface detector 110 is electricallyconnected to the power source unit 3 without twisting the electric wire41 a running through the rotary members 2 and 104 while the polishingpad shaft 104 turns.

The seal units 5 and 5 are disposed apart in the axial direction betweenthe retainer sleeve 21 or the outer circumference of the rotatorassembly 2 and the retainer portion 11 b of the second part 11 or theinner circumference of the joint block 1 surrounding the retainer sleeve21 concentrically, as shown in FIGS. 1 and 2. Between those inner andouter circumferences is formed a ring shaped seal space 50 with the twoends in the axial direction sealed.

Each seal unit 5 comprises a rotary seal ring 51 made of silicon carbidefixed in the outer circumference of the rotator assembly 2; a stationaryseal ring 52 made of silicon carbide held in the inner circumference ofthe joint block 1 and movable in the axial direction; a stoppermechanism 53 provided outside of the seal space 50 and engaging thestationary seal ring 52 for keeping the stationary seal ring 52 fromrotating while allowing the ring 52 to move in the axial direction; anda thrusting mechanism 54 provided outside of the seal space 50 to pressthe stationary seal ring 52 toward the rotary seal ring 51.

The rotary seal rings 51 and 51 of the seal units 5 and 5 are fixedopposite to each other with the retainer sleeve 21 providedtherebetween. The two rotary seal rings 51 and 51 are held and fixed bypressing the two sleeves 21, 22 with the flange 23 screwed at the lowerend of the main part 20 being tightened. The opposing end faces of thetwo rotary seal rings 51 and 51 form rotary seal end faces 51 a and 51 aor smooth surfaces perpendicular to the axis of the rotator assembly 2.

Each stationary seal ring 52 of the seal unit 5 is held in the outercircumference of the retainer section 11 b of the second part 11 via anO-ring 55 such that the seal ring 52 is movable in the axial direction,as shown in FIGS. 1 and 2. The stationary seal end face 52 a is sotapered and edge-shaped on the seal end face opposite to the rotary sealend face 51 a to form a ring-shaped contact face which comes into linearcontact with rotary seal end face 51 a. The diameter of the stationaryseal end face 52 a is set to nearly equal to the outside diameter of theretainer portion 11 b.

The stopper mechanism of the seal unit 5 is made up of one or morestopper pins 53 embedded in wall portion 11 a of the second part 11 ofjoint block 1, as shown in FIG. 2. This stopper pin 53 engages with anengaging hole 56 provided in the outer circumference of the stationaryseal ring 52 to keep the stationary seal ring 52 from rotating inrelation with the joint block 1 while allowing the ring 52 to be movablein the axial direction.

The thrusting mechanism in the seal unit 5 comprises a plurality ofcompressed springs 54 placed between the opposing end faces of the twostationary seal rings 52 and 52 at equal intervals in thecircumferential direction. Those springs press the stationary seal ring52 against the rotary seal ring 51 so that the stationary seal end face52 a is forced into contact with the rotary seal end face 51 a. Thesprings 54 are placed and held in spring retaining holes 57 that passthrough the wall portion 11 a of the second part 11 in the verticaldirection.

Thus the seal units 5 and 5 work to seal in the same way as the end facecontact type mechanical seal mentioned above. That is, the seal endfaces 51 a and 52 a come into relatively rotating and sliding contactwith each other as the rotator assembly 2 turns, to keep the seal space50 sealed at the two ends in the vertical direction. The dimensions ofthe components including the diameter of the tapered stationary seal endface 52 a are set so that when the relation of pressures inside andoutside the seal space 50 is reversed as the polishing solution feedingand discharge mechanism 107 is switched over to the negative pressuremode (for example when the fluid passage 7 is changed to the negativepressure or dry mode), the seal end faces 51 a and 52 a will maintain aneffective sealing function. That is achieved as by, for instance,bringing the balance ratio to zero.

The cooling unit 6 is formed in a space 60 between the joint block 1 andthe rotator assembly 2 but outside the seal space 50 and sealed with theseal units 5 and 5 and a pair of seal members 61 and 61, as shown inFIGS. 1 and 2. Into this cooling water space 60 is fed the cooling water62 to cool the contact portions of the seal end faces 51 a and 52 a inthe seal unit 5. The seal member 61, placed between the bearing 13 andthe rotary seal ring 51, seals a space between the opposingcircumferential surfaces of the joint block 1 and the rotary assembly 2.In the present example, the seal member 61 is composed of a seal ring 63made of an elastic material such as rubber, held in the innercircumferential surface of the join block 1 (in the innercircumferential surface of the support portion 10 a and 12 a of thefirst and third parts) and pressed against the outer circumferentialsurface of the rotator assembly 2 (the outer circumferential surface ofthe end portion of the main part 20 or the outer circumferential surfaceof the retainer sleeve 22); a reinforcing metal member 64 embedded inthe seal ring 63; and a garter spring 65 to keep an inner lip of theseal ring in contact with the rotator assembly. The joint block isprovided with an inlet 66 and an outlet 67 for cooling water 62 at theportions corresponding to the cooling water space 60 (in the connectingsections 10 b and 12 b in the first and third parts 10 and 12). Thecooling water 62 is fed continuously into the cooling supplying space 60through the inlet 63 to cool the seal end faces 51 a and 52 a of theseal unit 5.

The fluid passage 7 is a continuous path, made up of a first fluidpassage section 70 formed in the joint block 1 and a second fluidpassage section 71 formed in the rotator assembly 2, which communicatewith each other via the seal space 50 sealed with the seal units 5 and5, as shown in FIGS. 1 to 3. Passage 7 is connected to the slurry fluidfeeding and discharging passages 105 and 108 provided in pad shaftsupport block 103 and polishing pad shaft 104, respectively.

In other words, the first fluid passage section 70 is formed through thewall portion 11 a of the second part 11 in the radial direction, asshown in FIGS. 1 and 2. One end of the first fluid passage section 70opens at the seal space 50. The other end of the passage 70 opens at theouter circumferential surface of the second part 11, and is connected tothe slurry fluid feeding and discharge passage 105 on the non-rotaryside of the pad shaft support block 103. In this connection, the firstfluid passage section 70 in the second part 11 is formed and located soas not to interfere with the spring retaining holes 57 and the holes toreceive the stopper pin 53.

The second fluid passage section 71 is formed through the main part 20of the rotator assembly 2 and the retainer sleeve 21, as shown in FIGS.1 and 2. One end of the second fluid passage section 71 opens at theseal space 50. The other end opens at the lower portion of the main part20 and communicates with the slurry fluid feeding and discharge passage108 on the rotary side of polishing pad shaft 104 on which the rotatorassembly 2 is mounted. The second fluid passage section 71 in therotator assembly 2 is formed and located so as not to cross wiringconduit 24.

A surface polishing apparatus in which the rotary joint 101 thusconstructed is mounted can feed and discharge the polishing solution 106without causing such problems as described above. The polished surfacedetector 110 detects the state of the polished wafer surface 109 a on areal-time basis. On the basis of detected results, the polishingconditions can be controlled properly. Thus the surface of the siliconwafer 109 can be polished satisfactorily using this surface polishingapparatus.

At the time of polishing with the polishing pad shaft 104 being rotated,the polishing solution 106 sent out from the feeding and dischargemechanism 107 is allowed to flow through the slurry fluid feeding anddischarge passage 105 on the non-rotary side of the pad shaft supportblock 103 and then through the fluid passage 7 of the rotary joint 101to the slurry fluid feeding and discharge passage 108 on the rotary sideof the polishing pad shaft 104. In fluid passage 7, the first fluidpassage section 70 in the joint block 1 and the second fluid passagesection 71 in the rotator assembly 2 rotate relative to one another asthe polishing pad shaft 104 turns. But the seal space 50 connecting thetwo passage sections 70 and 71 is sealed with seal rings 51 and 52 ofthe seal unit 5, which slidingly rotate relative to one another. Thepolishing solution 106 flows through the fluid passage 7 without leakingfrom between two passage sections 70 and 71.

There is no concern that sticky substances in the polishing solution 106will adhere and deposit where the two seal rings 51 and 52 come intocontact with each other. That is, since seal end face 52 a of the secondseal ring 52 is tapered and edge-shaped, the sticky substances will bescraped and removed by seal end face 52 a. Thus, there is no possibilitythat the solid matter or abrasive grains in the polishing solution 106will intrude and deposit between the two seal end faces 51 a and 52 a.Therefore the two seal end faces 51 a and 52 a are kept in propercontact with each other without deterioration in their sealingperformance due to insufficient contact. Furthermore there is nopossibility that seal end faces 51 a and 52 a, which are cooled by thecooling water circulated through cooling water space 60, will heat upand seize.

It is also noted that two seal rings 51 and 52, made of a very hardmaterial silicon carbide, will not wear and generate particles incontact of the seal rings 51 and 52, unlike metal or carbon seal ringsor a combination of a seal ring made of a hard material like siliconcarbide and a seal ring of a soft material such as carbon, as in theordinary end face contact type mechanical seal. Therefore, there is nopossibility that wear dust or particles will be mixed in a polishingsolution 106.

Furthermore, the inside wall of fluid passage 7 is formed of a materialthat will not generate particles such as wear dust in contact with thepolishing solution 106 (abrasive grains in particular). That is, theportion (the second part 11) of the joint block where the first fluidpassage section of 70 is formed and the portions (main part 20 andretainer sleeve 21) of the rotator assembly where the second fluidpassage section 71 is formed are all made of a plastic material formachine parts, such as PEEK, PES, or PC, which is excellent indimensional stability and thermal resistance and further does notgenerate particles or dust in contact with abrasive grains. In thepresent example, PEEK is used in particular. Also, the seal space 50which connects the two fluid passage sections 70 and 71 is enclosed withthe inner circumferential surface of the retainer portion 11 b of thesecond part 11 and the outer circumferential surface of the retainersleeve 22, which form fluid passage sections 70 and 71, respectively,and the inner circumferential surfaces of the seal rings 51 and 52 allmade of silicon carbide, which is resistant to wear by abrasive grains.That precludes the possibility of producing dust particles by wearingdown the walls of the fluid passage 7 in contact with abrasive grainswhile a polishing solution 106 flows therethrough.

The stopper mechanism or the stopper pin 53 and the thrusting mechanismor the spring 54 are indispensable to secure a high sealing performanceby keeping the relatively rotating seal end faces 51 a and 52 a incontact under a proper pressure. If those component parts made of metalwere placed inside fluid passage 7, metal dust or particles produced byabrasive grains could be mixed into the polishing solution 106. In therotary joint of the present invention, however, the two mechanisms 53and 54 are provided outside the seal space 50, and no metallic partsthat are subjected to wearing in contact with abrasive grains, or whichhinder the flow of the polishing solution 106, are used in fluid passage7. That is, there is no possibility that fine metallic particles will beproduced by the flow of a polishing solution 106 in fluid passage 7.

For that reason, the polishing of wafer surface 109 a can be carried outwith satisfactory results, with the polishing solution 106 passingthrough the wellsealed fluid passage 7, without being mixed with fineparticles such as wear dust, and then jetting between pad head 104 a andsilicon wafer 109 from the slurry fluid feeding and discharge passage108 on the rotary side.

Another point to note is that the wiring path between the power unit 3and the polished surface detector 110 is divided into a stationarysection (an electric wire 42 a connecting the power unit 3 and thesecond connector 42) and a rotary section (an electric wire 41 aconnecting the first connector 41 and the polished surface detector 110)with the rotary joint 101 placed therebetween. The two sections areconnected by the rotary connector unit 4 such that the two sections arerotatable relative to one another, whereby there is no twisting of theelectric wire 41 a when the rotary section rotates as the polishing padshaft 104 turns. That permits mounting the polished surface detector110, an electric instrument, in the pad head 104 a that rotates, whichmakes it possible to monitor the polishing state of the wafer surface109 a and to control the polishing conditions properly. Thus ahigh-precision surface polishing will be possible.

Still another feature of the present invention is that at least thelower half of the casing 40 of rotary connector unit 4 is fit in thefirst cylinder 25 of the rotator assembly 2 with the casing being keptby the set screw 43 from relatively rotating. Hence, the portion nearthe center of gravity of the rotary connector unit 4 is held in therotator assembly 2. That can definitely prevent vibration of the rotaryconnector unit 4 due to rotation of rotator assembly 2, unlike thesystem in which the first connector 41 alone is held in the rotatorassembly 2 (the portion distant from the center of gravity of the rotaryconnector unit 4 is held in the rotator assembly 2). Load due to suchvibration therefore does not lessen the durability of rotary connectorunit 4. Furthermore the first connector 41 of the rotary connector unit4 is fit and held in the second cylinder 26 of rotator assembly 2. Thatcontributes to keeping rotary connector unit 4 from vibrating whenrotator assembly 2 turns.

When the polishing work is complete, fluid passage 7 is switched overfrom a positive pressure mode to a negative pressure mode or a dry mode.In negative pressure mode operation, too, there is no possibility thatseizure due to contact heat will be inflicted on seal end faces 51 a and52 a because the seal end faces are merely in linear contact with eachother, and besides the seal rings 51 and 52 are cooled with coolingwater 62.

It is understood that the present invention is not limited to theembodiment just described but may be changed or modified withoutdeparting from the basic principles of the present invention.

That is, it is also possible, needless to say, to apply the rotary joint101 of the present invention to CMP apparatuses different from thatshown in FIG. 3. An example of such CMP apparatuses is an apparatus inwhich the rotary table constitutes the polishing pad jetting thepolishing solution. The surface of silicon wafer is placed on and incontact with that pad table. The rotary joint 101 of the presentinvention is also applicable to a variety of apparatuses in which slurryfluids other than a polishing solution 106 are used. In suchapparatuses, the fluid blasting assembly is provided with an electric,electronic, optical, laser instrument, or the like, depending on thepurpose of operation, in place of the polished surface detector 110.Also, as an alternative to the electric wires 41 a and 42 a, a varietyof transmission media may be used depending on the purpose of operation,which include a metal cable and an optical cable (optical fiber). Inthat case, a suitable rotary connector unit 4 is selected according tothe transmission medium.

The rotary joint 101 of the present invention also can be adopted inrotary equipment handling corrosive fluids. That is, the material forthe walls forming the fluid passage 7 may be freely changed except forthe wall of silicon carbide formed on seal rings 51 and 52. Forequipment handling a corrosive fluid, a material that is resistant tocorrosion can be selected. Silicon carbide, the material forming theseal rings 51 and 52, is too hard to be worn in contact with abrasivegrains and is excellent in corrosion resistance and other properties,too. If, therefore, the parts of the fluid passage walls other than thesection formed by seal rings 51 and 52 are made of corrosion-resistantmaterials, then the rotary joint 101 may be used even in situations inwhich corrosive fluids are handled. In such situations, needless to say,a stopper pin 53 and spring 54 that are not positioned in fluid passage7 do not have to be made of a corrosion-resistant material. Thateliminates the necessity of making the stopper pin 53, spring 54, andother parts of a material that could compromise the intended functionsthereof just in order to secure corrosion resistance.

In case the fluid passage walls (except for the sections formed withseal rings 51 and 52) are to be formed of materials which are suitablefor the properties of the fluid, either of the following approaches ispossible. That is, the sections forming the fluid passage (in the aboveexample, the second part 11 of the joint block 1 and the main part 20and the retainer sleeve 21 of the rotator assembly 2) may all be made ofa suitable material. Or, the fluid passage walls only may be covered orcoated with that material. In case, for example, the rotary joint 101shown in FIGS. 1 and 2 is to be used in an apparatus handling acorrosive fluid, second part 11 of joint block 1, main part 20, andretainer sleeve 21 of the rotator assembly 2 are made of a suitablematerial such as, for example, stainless steel SUS 316 and SUS 304 underthe JIS standards designation. The inner circumferential surfaces of thefluid passage sections 70 and 71 and the surfaces (in contact with theseal space 50) of the second part 11 and the retainer sleeve 21 may becoated with a corrosion-resistant material. Among such materials arefluororesins such as PTFE, PFA, and FEP.

FIG. 2A illustrates an example in which the inside wall of the secondfluid passage section 71 is formed by a coating 20 a of PTFE coated ontothe surface of main part 20, made of stainless steel.

That is, in case the inner walls of the fluid passage are made up of aplurality of members which form the passage (in the above case, forexample, the second fluid passage section 71 is made up of the main part20 and the retainer sleeve 21), either of the following will do. Thatis, all the members which form the passage may be made of one kind ofmaterial. Or different materials may be used for each member forming thepassage. Or some of the members may be made of a material which isdifferent from the ones for the other members. The preferred materialsare plastic materials for machine parts, especially PEEK, PES, or PC.Similarly, in case the inner walls of the fluid passage or the fluidpassage wall surfaces are made up of a plurality of passage wallsections (in the above example, the inner walls of the second fluidpassage section 71 are formed out of the inner circumferential surfaceof the section passing through the main part 20 and that of the sectionpassing through the retainer sleeve 21), those inner walls may be coatedin either of the following. That is, all the passage wall sections arecoated with one material. Or a different coating material may be usedfor each of the passage wall sections. As coating materials, it ispreferred to use fluororesins materials such as PTFE, PFA, and FEP.

The seal unit 5 may be designed in any way except that care should betaken not to place the stopper mechanism 53 and the thrusting mechanism54 in the fluid passage 7. For example, the rotary seal ring 51 may beprovided in the joint block 1 while the stationary seal ring 52 (andauxiliary parts 53 and 54) may be placed on the rotator assembly 2. Alsothe rotary seal end face 51 a may be in a sharp-edge-shaped form.

As alternative to the rotation stopper set screw 43, other means such askey and spline may freely be used to keep the casing 40 of the rotaryconnector unit 4 and the rotator assembly 2 from rotating relative toone another.

What is claimed is:
 1. A rotary joint for fluids comprising: a jointblock; a rotator assembly mounted on a fluid blasting assembly which isforced to rotate and supported in the joint block such that the rotatorassembly is allowed to rotate, but is unmovable in the axial direction;and a rotary connector unit made up of a connector portion on astationary side connected to a power source unit and a connector portionon a rotary side electrically connected thereto such that the connectorportion on said rotary side is allowed to rotate relative to saidconnector portion on said stationary side, wherein a ring-shaped sealspace, sealed by a pair of seal units disposed apart in the axialdirection, is formed between an outer circumference of the rotatorassembly and an inner circumference of the joint block surrounding therotator assembly concentrically, wherein, in said joint block is formeda first fluid passage section with one end opening at the seal space andin said rotator assembly is formed a second fluid passage section withone end opening at the seal space and the other end opening at a placewhere said fluid blasting assembly is attached, whereby said two fluidpassages and said seal space form a continuous route of fluid passagesrunning through the joint block down to the fluid blasting assembly,wherein the connector portion on said rotary side is mounted in therotator assembly with said connector portion on said rotary side and therotator assembly sharing the same axis of rotation, a wiring conduitthat leads electric wire connected to the connector portion on saidrotary side to said fluid blasting assembly is formed so as not to crossthe second fluid passage section and the connector assembly on saidstationary side is mounted in the joint block to form a wiring pathleading from the power source unit to said fluid blasting assembly viathe rotary connector, wherein each of said seal units comprises: arotary seal ring and a stationary seal ring, both made of siliconcarbide, in which the rotary seal ring is fixed to the outercircumference of the rotary assembly and the stationary seal ring isheld in the joint block and is movable in the axial direction; and athrusting member which, placed outside of the fluid passages, urges thestationary seal ring against the rotary seal ring; and a stopper, placedoutside of the fluid passages, to prevent the stationary seal ring fromrotating while allowing the stationary seal ring to move in the axialdirection, and wherein said rotary seal ring and stationary seal ringhave opposing seal end faces and opposing seal end faces of the rotaryseal ring and stationary seal ring are tapered and sharp-edge-shaped soas to come in linear contact with the other, whereby a sealed spacesealed by the rotary seal ring and the stationary seal ring may besealed air-tight with the two seal end faces of the seal rings rotatingrelative to one another and sliding on one another.
 2. The rotary jointfor fluids as claimed in claim 1, wherein a space for supplying acooling water to cool contact portions of the seal end faces of therespective seal units is formed in an area between an outercircumferential surface of the rotator assembly and an innercircumferential surface of the joint block and outside said sealedspace.
 3. The rotary joint for fluids as claimed in claim 1, wherein theinside walls of the continuous route of the fluid passages are formed ofat least one machine part, said machine part being a plastic selectedfrom the group of plastics consisting of polyether ether ketone,polyethersulfone and polycarbonate.
 4. The rotary joint for fluids asclaimed in claim 1, wherein the inside walls of the continuous route ofthe fluid passage are coated with at least one corrosion-resistantmaterial selected from the group of materials consisting ofpolytetrafluorethylene, perfluoroalkoxy vinyl ether polymer andfluorinated ethylene propylene copolymer.
 5. The rotary joint for fluidsas claimed in claim 1, wherein said connector portion on said rotaryside is made up of a casing and a first connector fixed therein, saidconnector portion on said stationary side comprises a second connectorrotatably mounted in the casing, and at least part of said casing is fitin a first housing space formed in the rotator assembly with said casingand said rotator assembly being prevented from rotating in relation toeach other by a rotation stopper member provided on said casing.
 6. Therotary joint for fluids as claimed in claim 5, wherein a second housingspace communicating with the first housing space and the wiring conduitis formed in the rotator assembly, and a whole of said first connectoris fit into said second housing space.